body {
    background-color: #f8f9fa;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
}

.card {
    box-shadow: 0 0.5rem 1rem rgba(0, 0, 0, 0.15);
}

/* 为输入框添加一些样式，比如聚焦时的边框颜色等 */
.form-control:focus {
    border-color: #007bff;
    box-shadow: 0 0 0 0.2rem rgba(0, 123, 255, 0.25);
}